-
试验中选用IPG公司的光纤激光器,型号为IPG-YLS-10000,焊接头安装在六自由度机器人上,并用氩气保护焊接熔池。同时采用FLIR A615红外热像仪检测焊接过程中焊缝的温度变化信号。热像仪的分辨率为640pixel×480pixel,最小聚焦距离为0.25m,焦距比数为1.0,相频为50Hz。试验设备平台如图 1所示。
试验板材为304不锈钢,试样尺寸规格为100mm×40mm×5mm, 其化学成分和力学性能如表 1所示。活性剂选定SiO2、TiO2和NaF 3种AR(analytical reagent)级分析纯粉末。
Table 1. Chemical composition and mechanical properties of 304 stainless steel
type of steel mass fraction tensile strength/(N·mm-2) 304 stainless steel C Si Cr Mn Ni P S ≥520 ≤0.0008 ≤0.0100 0.1800~0.2000 ≤0.0200 0.0800~0.1100 ≤0.00035 ≤0.00030 -
采用红外热像仪对不同活性剂作用下激光焊接试样的熔池温度进行监测,对相应焊接过程建立有限元模型,并数值模拟其焊接温度场。对比分析数值计算与试验监测结果,揭示试样表面活性剂对激光焊接熔池温度场的影响。
-
试验采用两块304不锈钢板材对接在一起,将试样对接端面用精细锉刀修整至平整光滑,用夹具夹紧。活性剂涂敷至刚好遮住不锈钢表面金属光泽。待板材表面活性剂涂层的无水乙醇挥发后进行焊接试验。同时,采用红外热像仪对焊接过程中熔池温度的变化趋势进行监测。试验方案示意图及试验过程如图 2所示。通过正交试验得到一组较优的焊接工艺参量,具体数据如表 2所示。
Table 2. Welding parameters
parameter laser power P/W defocusing amount Δ/mm welding rate v/(mm·s -1) protective gas flow q/(L·min -1) shielding angle/(°) value 2500 -2 15 15 45 -
建立焊接过程热传导模型。由于焊接过程中热源高度集中且快速移动,焊缝区域温度梯度变化大,而远离焊缝区域温度梯度逐渐减小。因此,划分网格时采用非均匀网格,对焊缝区域的网格进行局部加密[7],网格划分模型如图 3所示。通过等效法建立活性剂模型,即将活性剂涂层贴合到已建立好的试件模型焊缝处,活性剂厚度为0.1mm,活性剂物理性能参量见表 3。温度场模拟中考虑不锈钢材料的密度、比热容和导热系数等热物理性能参量随温度变化的情况,具体数据引用参考文献中的不锈钢高温力学性能及高温物理性能指标。
Table 3. Thermophysical parameters of the active agent
type of active agent density/(mg·mm-3) thermal conductivity/(W·m-1·K-1) specific heat capacity/(mJ·mg-1·K-1) SiO2 2.27 1.4 0.966 TiO2 4.20 45 0.132 NaF 1.125 129.9 299.8 -
初始条件设为0℃,选择高斯热源模型,通过转化坐标的方式加载在试件模型表面[9]。实际焊接中,影响因素众多,为了简化模型,不考虑焊接过程中材料的相变潜热、汽化与电离,边界条件只考虑与空气的辐射和对流换热。
活性激光焊接304不锈钢温度场的数值与试验研究
Numerical and experimental study on temperature field of activated laser welding 304 stainless steel
-
摘要: 为了研究活性剂对激光焊接试样熔池温度的影响,以304不锈钢厚板为对象,建立了活性激光焊接的ANSYS 3维有限元模型,数值模拟其焊接温度场,并采用红外热像仪同步监测熔池温度变化情况。综合数值计算与试验检测数据,对比分析了涂覆不同活性剂及未涂敷活性剂的试件在激光焊接过程中的温度变化趋势。结果表明, 数值模拟结果与试验结果基本吻合,活性剂涂敷并未对温度场分布造成明显影响,但对熔池的峰值温度略有改变,相比未涂敷活性剂焊接试件,SiO2和TiO2活性剂使熔池峰值温度升高约7%~9%,NaF活性剂使熔池峰值温度降低约5%。此研究将丰富和发展活性激光焊接厚板的基础理论,为活性激光焊的推广应用提供重要理论和试验基础。Abstract: In order to study the effect of the active agent on the temperature of the molten pool of laser welding samples, the ANSYS 3-D finite element model of active laser welding was established with 304 stainless steel thick plate as the object. In the model, the welding temperature field was numerically simulated, and the infrared thermal imager was used to monitor the melting. Based on the comprehensive numerical calculation and experimental test data, the temperature variation trend of the specimens coated with different active agents and uncoated active agents during laser welding was compared and analyzed. The results show that the numerical simulation results are basically consistent with the experimental results. The application of the active agent does not have a significant effect on the temperature field distribution, but the peak temperature of the molten pool is slightly changed. Compared with the uncoated active agent welded specimens, SiO2 and TiO2 active agent respectively raises the peak temperature of the molten pool by about 7% to 9%, and the NaF active agent reduces the peak temperature of the molten pool by about 5%. This research will enrich and develop the basic theory of active laser welding thick plates, and provide important theoretical and experimental basis for the popularization and application of active laser welding.
-
Key words:
- laser technique /
- welding /
- 304 stainless steel /
- active agent /
- temperature field /
- numerical simulation
-
Table 1. Chemical composition and mechanical properties of 304 stainless steel
type of steel mass fraction tensile strength/(N·mm-2) 304 stainless steel C Si Cr Mn Ni P S ≥520 ≤0.0008 ≤0.0100 0.1800~0.2000 ≤0.0200 0.0800~0.1100 ≤0.00035 ≤0.00030 Table 2. Welding parameters
parameter laser power P/W defocusing amount Δ/mm welding rate v/(mm·s -1) protective gas flow q/(L·min -1) shielding angle/(°) value 2500 -2 15 15 45 Table 3. Thermophysical parameters of the active agent
type of active agent density/(mg·mm-3) thermal conductivity/(W·m-1·K-1) specific heat capacity/(mJ·mg-1·K-1) SiO2 2.27 1.4 0.966 TiO2 4.20 45 0.132 NaF 1.125 129.9 299.8 -
[1] KUO M, SUN Z, PAN D. Laser welding with activating flux[J]. Science and Technology of Welding and Joining, 2001, 6(1):17-22. doi: 10.1179/136217101101538497 [2] MEI L F, WANG Zh H, YAN D B, et al. Experimental study on active laser penetration welding of body galvanized steel[J]. Hot Working Technology, 2016, 45(17):31-34(in Chinese). [3] CHEN L, HU L Y, GONG Sh L, et al. Research on surfactant welding technology[J]. New Technology & New Process, 2005, 17(4): 39-41(in Chinese). [4] ZHANG R H, YIN Y, FAN D, et al. Numerical simulation of depth increasing mechanism of A-TIG welding[J]. Chinese Journal of Mechanical Engineering, 2008, 44(5): 175-178(in Chinese). doi: 10.3901/JME.2008.05.175 [5] ZHAO Y Zh, LEI Y P, SHI Y W. Effect of surfactant sulfur on flow pattern and depth ratio of weld pool[J]. Chinese Journal of Mechanical Engineering, 2004, 40(9): 138-143(in Chinese). doi: 10.3901/JME.2004.09.138 [6] DENG J Q. Simulation and experimental study on the dynamic behavior of laser deep welding keyhole and weld pool[D].Changsha: Hunan University, 2016: 14-18(in Chinese). [7] BALASUBRAMANIAN K R, BUVANASHEKARAN G, SANKARANARAYANASAMY K. Modeling of laser beam welding of stainless steel sheet butt joint using neural networks[J].CIRP Journal of Manufacturing Science and Technology, 2010, 3(1):80-84. doi: 10.1016/j.cirpj.2010.07.001 [8] WU X. High temperature mechanical and physical properties of stainless steel[D]. Lanzhou: Lanzhou University of Technology, 2010: 48-53(in Chinese). [9] HU L X, ZHOU D W, JIIA X, et al. Laser butt welding and numerical simulation of Zr-Sn-Nb-Fe zirconium alloy sheet[J]. Chinese Journal of Lasers, 2016, 43(7): 0702002(in Chinese). doi: 10.3788/CJL201643.0702002 [10] QUAN W W, LIU Sh H, LIU J L, et al. Experimental study on low power pulsed active laser welding of stainless steel[J]. Laser Technology, 2011, 35(3): 395-397(in Chinese). [11] PAN X D, LIU J H, BAO H T, et al. Effect of active agent on YAG laser-arc welding of stainless stell[J]. Aeronautical Manufacturing Technology, 2010, 53(11):92-95. [12] SU Y D. Research on thermal efficiency of laser deep fusion welding[D].Beijing: Beijing University of Aeronautics and Astronautics, 2000: 54-58(in Chinese). [13] MA L C, LIU J H, XIE Y Zh, et al. Preliminary study on the effect of laser welding activity on plasma[J]. Electric Welding Machine, 2005, 35(7):35-38(in Chinese). [14] LIU W Q, LI Y Q, LIU F D, et al. Effect of surfactant on weld defect of laser-arc composite welding[J]. Applied Laser, 2016, 36(3): 311-315(in Chinese). [15] LUO Y, XIE X J, HAN J T, et al. Effect of TiO2 active agent on acoustic emission of laser welding plasma in stainless steel[J]. Transactions of the China Welding Institution, 2016, 37(10): 109-112(in Chinese).